Modelling the dynamics of separation of the components of extractive phosphoric acid during its sorption purification using a modified acid retardation method
Abstract
The modified acid retardation method is one of the most promising methods for purification of components and separating a mixture of salts and acids in industrial processes. The development of theoretical concepts and the construction of mathematical models that can be used to study the process with a different choice of modes of implementation is a necessary step towards its optimization.
In this study, a mathematical model of the phenomenon was proposed, the key features of which are taking into account chemical equilibrium in a multicomponent system and taking into account the inhomogeneous nature of the solution zone inside micropores. Namely, a region near the polymer filaments of the gel sorbent was identified. In this region dipole forces act on the molecules, leading to a change in the concentrations of the components, and, accordingly, changing the equilibrium ratios between different parts of the solution in micropores and the amount of the sorbed substance.
Based on the proposed model, a computer program that allows to carry out numerical calculations and compare them with experimental data was implemented. The model was tested for the results of experiments on the purification of extractive phosphoric acid by a modified acid retardation method, which is applicable to mixtures with poorly soluble components. The experimental curves of output concentrations have a specific form, the key features are the presence of sharp peaks in salt concentrations, the slope of the output curves during washing, etc. It was found that when selecting a certain, small number of coefficients, the model reproduces the entire set of characteristic indicators of the output data with an accuracy not lower than the experimental one and thus makes it possible to determine the sorption characteristics. The proposed model can be used to describe the dynamics of the process in other solutions and sorbents with appropriate modifications.
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References
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